Electrical transposition system



Nov. 26, 1929.

Lil/Le l H. A. AFFEI.

ELECTRICAL TRANSPOS ITION SYSTEM Original Filed Aug. 3l, 1922 ATTORN EYPatented Nov.` 26, 1929 l UNITED STATES,

PATENT o1-Fica HERMAN A. AFFEL, 0F MAPLEWOOD; NEW JERSEY, ASSIGNOR TOAMERICAN `PHONE AND TELEGRAPH COMPANY, A CORPORATION OF NEW LYORK'ELECTRICAL TRANSPOSITION SYSTEM Original application flied August 31,1922, Serial No. 585,436, Patent No. 1,530,537, dated March 24, 1925.`Divided and this application led March 9, 1925.' Serial N'o. 14,312.

This invention relates to electrical transposition systems andparticularly to an arrangement for transposing a line circuit adaptedfor the simultaneous transmission of a plurality of frequencies or bandsof frequencies.

This application is a division of my copend- Aing application, SerialNo. 585,436, filed August 31, 1922, which issued on March 24, 1925, asPatent No. 1,530,537.

Heretofore in the operation of systems in which signaling was carried onby means of a relatively low frequency current or range of low frequencycurrents such as required for voice transmission, where it has beennecessary to transpose pairs of wires to prevent mutual interactions,due to inductive or. capacity effects between them, it has beencustomary to introduce the transpositions at intervals which were shortrelative to the wave lengths of the electric currents concerned. Thishas usually entailed no particular hardship, since, as noted-above, the

frequencies were relatively low and the wave len hs correspondinglylong.

en transposing wires to prevent mutual interactions, or in other wordscrosstalk, be

` short and in order to carry out the general principle of providingtransposition intervals which are a small fraction of the wave length,requires, in many cases, the insertion of transpositions at pointsextraordinarily close together. In fact the number of transpositionsrequired and the physical difiiculty involved in obtaining the accuratefrequency spacing, often renders it impracticable to employ such anarrangement, effective throughout a wide range of frequencies. A lessernumber of transpositions may, however, be provided where it is desiredto have the action eEective only atA a single frequency or over arelatively narrow range of frequencies because in this case therapidphase changes act in a sense to transpose the currentsautomatically at frequent. intervals.

` between circuits throughout a wide range of frequencies, covering lowfrequencies as well as high frequencies, with a minimum number oftransposition points. The particular feature by which this objective isachieved is the use of ywhat may be termed selective transpositions,namely, means whereby a line circuit may be effectively transposed at agiven point for a particular frequency, or band of frequencies, and atYthe same time rendered untransposed at the same point for other bands offrequencies than those for which it is desired to transpose the saidline at that point. By this means a complete transposition system,effective throughout the desired wide range of frequencies, maybe`provided by superposing the designs of a plurality of transpositionsystems, each of itself relatively simple, involving a minimum oftranspositions and effective fora portion of the total frequency rangeinvolved. The points at which transpositions are required for one partof the range and not for another part of the range are effectivelyprovided for by a selective transposition as above noted, the points atwhich both circuits are required to be transposed being served by asimple transposing of the Wires in the ordinary manner.

Other objects of this invention will be apparent from the followingdescription when read in connection with the attached drawing, in whichFigure 1 shows a simple form of embodiment of the invention, Fig. 2shows the application to a line circuit of a plurality of units such asare shown in Fig. 1, and Fig. 3 shows the application of the inventionto a directive radio antenna.

In Fig. l, 1 and 2 represent two sections of a line which is adapted tohave transmitted thereover a plurality of frequencies, or bands offrequencies. Inserted between the sections 1 and 2 of the said linecircuit, and in series therewith, is an electrical network which may betermed, for the purpose of description, a transposition group.

line into different bands,-thereby permittin the circuit carrying one ormore of the ban s to be transposed, while maintaining in the circuitcarrying the remainder of the frequencies, the normal disposition of thewires. This arrangement thus provides the selective transpositionpreviously referred to.

This network consists in a plurality of filters connected in parallelelectrically with each other, thereby affording a plurality of pathsbetween the sections 1 and 2 of the'said line circuit, through which theplurality of frequencies, or bands of frequencies traversing the saidline must pass. While only two filters have been shown in the group inFig. 1, it is to be understood that 'the invention is not limited tothis particular number, but may be varied without changing the scope ofthe invention. The filter designated A is of the type known in the artas a band-suppression filter and is disclosed in the patent to G. A.Campbell, No. 1,493,600, dated May 13, 1924. This filter, thetransmission frequency characteristic of which is represented by thedotted curve a in Fig. 1", is adapted to suppress a particular band offrequencies such, for example, as that represented by f1-f2 and totransmit readily, or substantially so, all frequencies lying withoutthat band. This is clear from a consideration of Fig. 1, which shows thevariation of loss of the network A for various frequencies impressedupon the said network. Thus, it will be seen that for frequencies belowf1 and above f2, the transmission loss is fairly low, whereas it is veryhigh for the band lying between f1 and f2. The filter B, whosecharacteristic curve is designated b in Fig. 1, is of the type known asband-pass filters. This filter, with the exception of the transpositionof the conductors designated 3, is disclosed in the patent to G. A.Campbell, 1,227,113, dated May 22, 1917. A consideration of thecharacteristic curve shown in Fig. 1"l shows that the transmissin lossto currents below f1 and above f2 is very great, whereas thetransmission loss lylng between these limiting frequencies is relativelysmall.` This means, of course, that the band f1--f2 will be readilytransmitted through a filter of the type rep resented by B, but thatfrequencies or bands of frequencies lying without those limits will besubstantially sup ressed. Since filter A sup resses the same and offrequencies which 1s readily transmitted by filter B, these filters aretermed complementary and are hereinafter referred to by that term. Byreversing the conductors of the filter B at the point 3, the line iselectrically transposed with respect to the currents that aretransmitted through the filter B, but the line is not transposed withrespect to currents of the frequencies transmitted through the filter A.It will be clear, therefore, that if, for example, a band of frequenciesf1-f2 and another band of frequencies lying without the range of the said first band, arrive over the section 1 ofthe line circuit, the bandf1-f2 will be transmitted through the filter B and, due to thetransposition 3, will be impressed in an opposite sense across thesection 2 of the said line circuit. The other frequencies will not passthrough the filter B, but will be transmitted through the filter A, andsince the conductors thereof are not reversed, the said other band offrequencies will be impressed across the section 2 of the line in thesame sense in which they were impressed across the line 1.

The application of a plurality of transposition groups, such as shown inFig. 1, is illustrated in Fig. 2. In this figure, 1, 2, 3, 4 and .5represent five sections of a line circuit which 'are connected togetherby means of a plurality of transposition groups, the object of which isto transpose the said line for a particular frequency, or band offrequencies in order to prevent cross talk into some adjacent pair ofwires. Let it be assumed that the points X and X1 represent points atwhich it is desired to .transpose to prevent cross talk for frequencieslying within the band f1-fz and Y and Y1 represent desired transpositionpoints for preventing cross talk for frequencies lying within the bandfs-. ThereV should accordingly be inserted at X and X1 a transpositiongroup comprising a -filter`B adapted to transmit the band of frequencies)t1-f2 and to suppress all other frequencies, and a filter A which willtransmit all of the said other frequencies and will suppress the bandf1-f2. The transposition group shown at Y and Y1 comprises a filter D,which is adapted to transmit the band of frequencies f1-f4 (viz. thesaid other frequencies transmitted by the filter A at points X and X1)but to suppress the band )f1-f2, and a filter C, which is adapted totransmit the band )c1-f2, but to suppress the band fS-f1. Each of thefilters B and D has its conductors reversed as represented by 3 inFig. 1. Accordingly, it will be seen that if two hands of frequencies,for example, )i1-f1 and f3-f4 arrive over the section 1 of the saidline, the band f1-f2 will 'be transmitted through the filter lB and willbe impressed across the line 2 in an opposite sense. The band )cf-f1will be transmitted through the filter A and impressed across thesection 2 in the same sense'in which it was impressed across thesection 1. These two bands will then be impressed across thetransposition group at Y. The band 7f3-f1 will be transmitted throughthe filter D and. due to the transposition therein, the band will beimpressed across the section 3 in an opposite sense to that in which itwas impressed across section 2. The band )f1-f2 will be transmittedthrough the filter C and impressed across section 3 in the same sense inwhich ,10 to 15 inclusive.

it was impressed across section 2. Accordingly, it will be seen that theline, which iS made up of a plurality of sections designated, forexample, 1 to 5 inclusive, is transposed at the points X and X1 forcurrents of the band fl-fg. but is not transposed for all otherfrequencies. At points Y and Y1 the said line is transposed for currentsof the frequencies 7f3-f, but is not transposed for currents of otherfrequencies. L

It will he apparent that any number of transposition groups may be usedin aline such as shown in Fig. 2. depending upon the number of bands offrequencies for which it is desired to transpose the said line.

The arrangement shown in Fig. 3 represents the application of thisinvention to a directive loop antenna, the object of which is to makethe antenna better responsive to waves received from a particulardirection. 1H my Patent No. 1,615,896, that issued on February 1, 1927,I showed the use of a transposed loop antenna, which, by the properlocating of the transposition points, was better adapted to receivewaves of a particular fre uency, or band of frequencies, and to exclu eor suppress currents of other frequencies. Such an arrangement, as wastherein disclosed, tended to minimize the effects of static and also ofinterference from stations other than that from which it was desired toreceive signals. The arrangement shown in Fig. 3 is an application ofthe present invention to the antenna broadly shown and claimed in thesaid copending application. In Fig. 3, the antenna per se is representedby a plurality of sections designated Across the one end of section 1()is a terminating resistance 16, which simulates the characteristicimpedance of the antenna. The other end of section 10 is connected withthe filters A and B, the filter B being designed to transmit. forexample. the band f1 f2 and filter A being designed to suppress thatfrequency but to transmit all other frequencies. By the proper locationot' the transposition groups at the points X. X,. X2 and X3 the antennais made highly selective for frequencies lying within the desired bandand is made non-selective for other frequencies.

vhile l have shown tivo uses to which my invention may be applied, itsscope is notv so limited. since many other and varied uses will occur tothose familiar with the art. Furthermore. while 1 have shown the use ofband fillers of various types -in the drawing in which the invention isembodied, and have described these particular types of filters in thespecification." it must be understood that the invention is not limitedto these particular types of filters. Nor is it limited to thetransmission of hands of frequencies since the invention is applicableto the transposition of a transmission circuit for a plurality of singlefrequencies as well as `for bands of frequencies.

Although this invention has been disclosed in a particular form it iscapable of einbodiment in other and different forms Within the spiritand scope of the appended claimsl What is claimed isz' 1. An antennahaving a plurality of groups of frequency selecting devices connected atpredetermined intervals therein. the devices of each group being inparallel and so designed and adjusted that the frequency selected by onewill be that suppressed by the other.

2. A loop antenna having inserted therein at predetermined intervals aplurality of groups of frequency selecting devices, the devices of eachgroup being in parallel and complementary in nature whereby thefrequencies selected by one device will be those suppressed by theother, the conductors of the said antenna being transposed for theselected frequenciesat each point of connection of the said groups withthe said antenna, and

transposed at its midpoint for the nonselected frequencies.

3. In a radio signaling system, the combination with an antenna adaptedto transmit a plurality of bands of frequencies, of a group of filtersinserted between sections of the said antenna, the said filters beingconnected in parallel and being of the complementary band-pass andband-suppression types, the band-pass lter having its conductorstransposed whereby the said antenna will be transposed at that point forthe frequencies transmitted through the said band-pass filter.

4. In a radio signaling system` the combination with an antenna adaptedto transmit a plurality of frequencies. of a group of filters arrangedin parallel with each other. the said group being inserted betweensections of the said antenna. one of said filters being adapted totransmit readily one of the said frequencies and to suppress otherfrequencies. and the other of the said filters being adapted totransrnitsaid other frequencies and to suppress the said first-mentionedfrequency, the said antenna being transposed through the saidfirst-mentioned filter.

5. In a radio signaling system. the combination `with a. loopy antenna,of groups of filters connected therewith. each group comprising aband-pass and a band-suppression filter of complementary types. the saidbandpass filter of each group having its conductors transposed. therebyeffecting a transposition of the antenna at that point for thefrequencies passed bv the said filter. the said groups being spacedalong the said antenna at intervals representing a transposition sectionfor the frequencies passed b v the said band-pass filter of each group,

6. An antenna effectively transposed at certain points for predeterminedfrequencies but eiectively non-transposed at those points for otherfrequencies.

7. An antenna, transposed at its midpoint 5 to neutralize interferingfrequencies, and effectively transposed at'other points for certain ofsaid frequencies but effectively nontransposed at lthe said other pointsfor other frequencies. lo 8. An antenna rendered selective for a certaingroup of frequencies by being transposed at certain points along itslength and at the same time non-transposed at the said certain pointsfor other frequencies than those of the said certain roup.

In testimony Whereo I have signed my name to this specification this 6thday of March, 1925.

A HERMAN A. AFFEL.

